Control system for electric motors



June 16, 1931. C J. H. HALL 1,809,847

CONTROL SYSTEM FOR ELECTRIC MOTORS I Filed Jan. .28, 1926 lock 4$ IN VENTOR. BMW M A TTORNEY Patented June 16, 1931 UNITED STATES PATENT OFFICE JAY H. HALL, OF CLEVELAND HEIGHTS, OHIO, ASSIGN'OR TO THE ELECTRIC CON- TROLLER & MANUFACTURING- OOMPANY, OF CLEVELANRQHIO, A. CORPORATION OF OHIO conrnor. sysrm r03. rmnc'rnrc Morons Application filed January. 28, 1926. Serial No. 84,290.

the control of electric motors by dynamic braking. I

It is one object of this invention to provide for a synchronous. motor a'dynamicbrakingsystem which is quickly responsive to emergency control in case of accident to an operative of machinery driven by the motor. Other objects pertaining to portions of the system are set forth hereinafter.

Referring to the accompanying drawings, Fig. 1 is a diagrammatic view of the said system with the' motor at rest.' Fig. 2 is an end View of the main switch 6 and adjacent parts, looking at Fig. 1 from the left. Figs. 3 and 4 show diagrammatically two modifications of the tripping devices for the main switch.

Referring first to Figs. 1 and 2, 1 designates the armature of a synchronous motor having the field winding 2 sup-plied with current from a D. C. source through the electromagnetic contactors 3 and.4 operated by current in the winding 5.

6 is'a switch having the movable member 7 carrying contacts 8 and 9 which in the running position of the switch engage the fixed contacts 10 and 11 and thereby connect the supply lines L and L3 through the resistances 12 and 13 to two of the motor leads, the

third supply line L2 being simultaneously connected to the thirdmotor lead through the contacts 14 and 15, as hereinafter explained.

16 and 17 are electromagnetic acceleration contactors operated by current in the winding 18 to shunt the current from lines L and L3 around the resistances 12 and 13, the winding 18 being controlled by the lockout switch 19.

When the switch 6moves to running position the electrically connected contacts 20 and 21 on the member 7 engage the fixed contacts 22 and 22', and when the switch 6 moves to braking position the contacts 8, 9 and 21 on the member Tengage the fixed contacts 23, 23 and 24. When the switch 6 is in running and braking positions the contacts 25 and 26 are in contact, and the contacts 14 and 15 remain closed during the braking connection of the motor. 1

The mechanism for operating the switch 6 is shown in Fig. 2, now to be described. The

U-shaped frame 27 has at opposite sides of the space between its side members the fixed bars 28 and 29, the former supporting the contacts 10, 11, 22 and 22, and the latter the contacts 14, 23, 23', 24.and 25. The frame carries the pole pieces 30 energizable by the winding 31 for causing the armature 32 pivoted on theframe at 33 to move toward themselves. The armature carries the support 34 on which the contacts 15 and 26 are mounted.

The armature 32 carries the arm 35 pivoted thereto'and carrying the member 7 at its upper end. The arm 35 and a fixed point beneath the bar 28 support the end pivots of two toggle links 36 flexed downwardly, the 'pivot connecting their adjacent ends carrying the rod 37 resting on the helical spring 38, the lower end of the spring being supported by the arm 39 projecting from the hub of the armature 32. v

The frame 27 supports the tripping lever 40 having one end provided with a catch for interlockin with the horizontal hook 41 carried by the toggle mechanism. The other end of the lever 40 lies over the plunger armature 42 in the trip coil 43.- The trip'lever 40 holds the hook normally at such a position that, when the armature 32 is actuated the switch member 7 will move to running position and be held thereby the trip lever. The operation as to Figs. 1 and 2 is as follows, the parts being initially as on these figures. Upon closing the starting push-button switch 44 current flows in arallel circuits including in one circuit t e winding of the relay 45 and the upper auxiliary contacts of the contactor 4, and in the other the winding 31, the contacts of the stopping push-button switch 46 andthe time relay 47. Current in the said windings causes the armature 32 to be actuated, the switch 6 to be moved to the running position, and the relay 45 to be closed somewhat later owing to the dash-pot 48. The line L is connected to the armature through the contacts 8 and 10, the resistance 12 and the winding of the switch 19; the line L2, through the contacts 14 and 15; and the line L3, through the contacts 9 and 11 and the resistance 13.

During the period between the energizing of the coil of the relay 45 and the closing of the same and of the contactors 3 and 4, the

armature 1 is supposed to have been started in the usual manner with the field winding temporarily shorted through a suitable resistance 59. The relay 45 is made to close so,

-ors 3 and 4 to close and connect the field winding .2 to a source of D. C. current, the

saidshort-circuit including the field winding having been plreviously opened as in the usual practice. he short circuit of the field winding during the starting of syn chronous motors is made through the reslstance 59 and the contactor 3 and the back contact 60.

Upon the closure'of the contactors 16 and 17 the motor is connected to full voltage through the contacts 8-10, 911, and 14-15 and accelerates to approximately synchronous speed.

The closing of the relay connects the winding 5 in a shunt around the winding of the relay, whereupon the contactors 3 and 4 close, connecting the field winding 2 to a source of direct current and in series with the field rheostat 49. When the contactor 4 closed it opened its upper auxiliary contacts, thereby opening the circuit of the winding of the relay 45, which now drops open.. The contactor 4 also closed its lower auxiliary contacts, thereby connecting the winding 5 in a maintaining circuit for the contactors 3 and 4. In order to prevent the release of the relay 45 from opening the circuit of the winding 5, the switch 6 upon moving to its running position closed the contacts 25 and 26 which like the relay 45 connects the winding to the line L2.

To stop the motor the push-button switch 46 is opened, thereby opening the circuit of the winding 31, whereupon the switch 6 opens and moves under the pressure of the. spring 38 to the intermediate position shown in the drawings, and the contactors 3 and 4 open owing to the separation of the contacts 25 and 26. The contactors 16 and 17 also drop open because the circuit of the winding 18 is broken by the contact 21 leaving the'contact 22'. The lock-out switch 19 was already open, as its winding was short-circuited by the contactor 16, the winding 18 being kept in circuit by the auxiliary contacts of the contactor 16, which were closed when this contactor'closed.

51 is an emergency switch located conveniently for operation in case of an emergency requiring the stopping of the motor. This switch turns on, t by the handles 53 and connects the winding of the relay 54 across the lines L2 and L3. If, when the motor is running, the switch 51 is o ened, the relay 54 closes a circuit through t e trip coil 43 and the contacts 20 and 22, whereupon the plunger armature 42 is caused to rise and disengage the trip lever 40 from the hook 41, permitting the spring 38 to straighten out the toggle links 36 and e pivot 52 and is operated force the switch 6 to its braking position, in i which the contacts 8, 21 and 9 engage the contacts 23, 24 and 23, respectively. The contacts 14 and 25 remain closed on the .contacts 15 and 26, respectively, because the a'rmature 32 which carries the contacts 15 and 26 remains closed. The armature windings are now connected in closed dynamic braking circuits with the resistance 24'. As the field winding 2 re,

mains energized, the motor is brought qu ckly to rest.

When the switch 6 is in braking position,- the windmg of the time relay 47 is in a closed The switch 6 then moves to its openor intermediate position, the contactors ,3 and 4 open, and the relay 47' drops to its normal posltion. The contactors 16 and 17 opened when the switch went to braking position as they do when it goes to open position.

The relay 54 is moved to open position as soon as the switch 51 is closed by the springs 58. As long as the relay is closed the motor cannot start because the actuation of the armature 32 upon closing the switch 44 merely causes the braking position of the switch 6 to be reassumed, since the coil 43 will be energized and cause the tripping lever 40 to be tilted out of interlocking position with the hook 41. This ensures that the motor can not be started as long as the emergency swltch is released which presumably will not occur until the emergency has passed.

' In Fig. 1 a resistance 59 is connected in a' closed circuit with the field winding 2 through the back contact 60 of the contactor 3, so that, when the contactors 3and 4 open the field circuit, the field winding will be connected in the said closed circuit to furto lift the outer end of the trip lever 40 and ull it out of interlocking position with the 00k 41 whenever current is out off from the winding 43 by the opening of the emergency switch 51.

In Fig; 4- the parts are the same as in Fig.

' 3, except that the up-pulling spring 56 in the latter is replaced by an up-pushing spring 57 in the former, the lower end of the winding being connected directly tothe line L2.

This application shows, but does not claim the subject matter claimed in applicants application Serial No. 317 ,082, filed November 3, 1928.

I claim 1. In a controller for synchronous motors, a source of alternating current su ply, a source of direct current supply, a raking circuit, electro-responsive means for effecting the connection of the motor armature to the source of alternating current'supply and forsubsequently effecting the connection of the motor field to the source of direct current supply when the motor has accelerated to approximately synchronous speed, means operated by the said eleotro-responsive means for setting up a bias for disconnecting the armature from the alternating current source of supply and connecting itto the braking circuit, a safety switch, and means depending upon current flowing in the safety switch for preventing the bias from becoming effective for the purposes described.

2. In a controller for synchronous motors, separate sources of current supply, a braking circuit, electro-responsive means for effooting the connection of the motor armature and field windings to the respective separate sources of supply, means made effective by the said electro-responsive means for disconnecting the armature fromits source of supply and connecting it to the braking circuit, a normally closed safety circuit, and means whereby a failure of current in the safety circuit causes the electro-responsive means to become effective for disconnecting the armature from itssource of supply and connecting it to the braking circuit.

3. In a motor control system, a motor, a

source of current supply, a stopping circuit, a

set of contacts, an electromagnetic device for moving said contacts for connecting the armature of the motor to the said source, biasing means effected by the said electromagnetic device for moving said contacts to disconnect the armature from its source of supply and connect the armature to the stopping circuit, a safety circuit, hold ng means for said biasing means made efiectlve by the safety circuit, and means whereby a failure of current in the safety circuit causes'the' electro-magnetic device to disconnect the armature from the source and connect it to the stopping circuit. 1

4. In a control system, a source of alterconnecting the motor armature to the source of alternating current supply for running the motor, a second set closed by the device and thereby connecting the motor armature to the electrical load element and thereby brakin the motor, and a third set of contacts closed y the device in both the running and braking positions and thereb effecting the connection of the motor fiel to the source of direct current supply subsequently to the closure of the first set of contacts.

5. In a motor system, a synchronous motor, a source of alternating current supply, a source of direct current supply, an electromagnetic device for connecting the motor armature to the source of alternating current supply and for subsequently connecting the motor field to the source of direct current supply, an operating control circuit, a master switch connected to the control circuit for suppliy.

6. n a controller for synchronous motors, a source of alternating current supply, a source of direct current supply, a braking circuit, electro-responsive means for effecting the connection of the motor armature to the source of alternating current supply and the motor field to the source of direct current supply, means operated by thesaid device for setting up a bias for disconnecting the armature from the alternating current source of supply and connecting it to the braking circuit, and means for causing the said bias to become effective and disconnect the armature from the alternating current source of supply without disconnecting the motor field from' the direct current source of supply, in combination with a normally closed safety circuit and means whereby a reduction of current in the safety circuit below a predetermined value causes the electro-magnetic device to operate the controller from the running position to the stopping position.

7 In a motor control system, an electric motor, a normally-open running circuit for the motor, a normally-open stopping circuit for the motor, a normally open circuit, means controlling the latter circuit and controlled thereby to effect the connection and disconnection of the motor with respectto the said the motor has come to rest.

running and stopping circuits, a normallyclosed safetyv circuit, and means whereby a reduction of current in the said safety circuit below a given value causes the motor to be disconnected from the running circuit and connected to the stopping circuit,f and means for opening the stopping cir'cuitwhen 8. In a control system,- an electric motor,

. a stepping circuit for the motor, a controller having a running position for connecting-the rent power circuit, and means for automatically disconnecting the field from the direct' current power circuit when the motor has come to rest.

11. In a control system, a source of electric current supply, an electric motor, a running and a stopping circuit for the motor, a controller having a running position for a connecting the motor to the source of supply,

motor to a source of supply, a sto ping posia stopping position for connecting the motor tion for connecting the motor tot e stopping\t0 the stopping circuit, and an off position circuit, and an off position having both circuits open, an electro-magnetic device for operating the controller, a normally-closed emergency circuit, and means whereby a failure of current in the said emergency circuit causes the said electro-magnetic 'device to operate the controller to disconnect the motor I from the source of supply and connect the motor to the said' stopping circuit.

' 9. In a control system for synchronous motors, an alternating current power circuit for the motor armature, a direct current'power circuit for the motor field, a stopping circuit, a double-throw contactor with normally-open contacts, a winding for operating said contactor to connect the motor armature to the alternating current power circuit and for effecting a delayed connection of the motor field to the direct current ower cir'cuit, means for operating the dou le-throw contactor to disconnect the motor armature from the alternating current power circuit and connect it to the said stopping circuit, a norm'ally-closed safety circult, and means whereby upon the failure of current in the said safety circuit the motor armature is disconnected from the alternating current power circuit and connected to the stopping circuit while the field winding is still connected to the direct current power circuit.

10. For the control of a synchronous motor, alternating current and direct current power circuits, a stopping circuit, a set of normally open power contacts for connecting the motor armature to the alternating cur rent power circuit and the motor field to the direct current power circuit, a set of normally-open stopping contacts for connecting the motor to the stopping circuit an electromagnetic device for closing the alternating current power circuit and for effecting a de layed closure of the direct current field circuit, a pressure actuating mechanism operated by the electro-magnet which when pressure is released disconnects the motor armature from the alternating current power circuit and connects it to the stopping circuit, a normally-closed emergency circuit, and means whereby a reduction of current below a given value in the emergency circuits ef-' fects the release of the said mechanism to for opening the running and stopping circultsand an operating control circuit and instrumentalities controlled by the latter circuit for closing two sets of contacts which are open at the off position, one of the said sets of contacts to close the running circuitof the motor in the running position only and the second set of contacts to close the stopsignature.

' JAY H. HALL. 

